Floating roof tank



March 22,1949. Y J. w. ALLEN l 2,464,786

FLOATING ROOF TANK Filed NOV. 3, 1945 2 Sheets-Sheet 1 22,1949. J, w ALLEN 2,464,786

FLOATIUG ROOF TANK 4 l Filed Nov. 3, 1945 2 Sheets-Sheet 2 ltented Mar. 22', 1.949

s i PATENT OFFICE l FLoA'rmG Boor 'TANK John W. Allen, Chicago, Ill., assignor to Chicago Bridge & Iron' Company, a corporation o! Illinois Appucation'uvember 3, 1945, serial No. 626,584

11 claims. (el. 22o-2s) This invention relates to a floating rooftank and particularly to an improved roof structure for such tanks.

Floating roof tanks are used for the storage of volatile liquids, and are designed so that the.

roof floats on top of the stored liquid. Thus the root rises and falls as the liquid contents of the tank are increased and decreased. I have invented and improved floating roof wherein all sur.- faces on the bottom of the roof are in contact with the stored liquid. This eliminates the vapor space and substantially lessens or prevents the usual corrosive effect. y

The new floating roof comprises a plate-like structure normally floating on top ofv the liquid. There is provided an upstanding rim member around the plate-like structure adiacentthe shell of the tank. The plate-like structure isformed with a low portion-which serves as a drain basin. The rest of the structure slopes toward this drain portion so that any water falling on the tank will now to the drain and can then be conducted to the outside of the tank. Air-tight pontoonsare positioned around this lowest drain portion with-the pontoons being located above the liquid contacting portion of the structure. Drain channels are provided in the areas between the pontoons, and these channels slope to the lowest drain portion in order to carry oi rain water. If vapor should build up under the oating roof it is preferred that it be equally distributed, and this equal distribution of vapor is provided for by arranging interconnecting vapor lines connectingfthe highest portions of the plate-like structure.

When there is no liquid load of rain water on top of the roof the pontoons are in inoperative' position above the liquid contacting portion of the roof. If the drain which is normally provided in roofs of this type is choked up and does not operate, then the pontoons help maintain thebuoyancy of the roof. There are no separate vapor spaces-per se provided in the roof. but it vapor should form between the stored liquid and the bottom of the roof the pressure oi the vapor will be substantially uniform under the entire area, thus eliminating any ilexing. It vapor does form it would tend to collect under the highest portions oi' the roof bottom. and itis preferred that` a vapor line be provided interconnecting these highest portions. Because the bottoms of the .pontoonsl are level with the liquid surface thev pontoons cannot iill with stored liquiddue to a leak in one or more pontoons,y except under an emergency load of rain water`or the like on the deck. This emergency4 load will be of short duration 'so that very little of the stored liquid will ow into a leaky pontoon.

The invention will be described as related to the embodiment shown in the accompanying drawings. Of the drawings Fig. 1 is a plan view oi.' the roof embodying the invention; Fig. 2 is an enlarged vertical section taken along the curved line 2-2 of Fig. 1; Fig. 3 is a vertical section taken through the entire tank including the roof, with the roof section being along line 3-3 of Fig. 1; and Fig. 4 is an enlarged vertical section taken along curved line 4-4 of Fig. 1.

In the embodiment shown in the accompanying drawings the storage tank comprises a substantially cylindrical shell I0, a roof il therein iloating on top of the liquid contents l2 of the tank. Any desired seal I3 may be provided between the edge of the roof il and the shell lil.

The floating roof il is substantially circular in shape and comprises a plate-like bottom Il in contact with the liquid I2 and an upstanding rim portion` I5 around the edge. At the center of the bottom Il ofthe roof structure there is provided a lowermost portion i6 serving as a drain. A hinged drain pipe l1 connects the bottom of the drain I6 to the outside of thetank. Any suitable draining means maybe provided.'

Located on top of the liquid-contacting portion of the roofare radial pontoons IB extending from the central drain Ii to the rim I5 of the roof. The tops oi' the pontoons are substantially even with the top edge of the rim I5, and the v bottoms of the pontoons are substantially horizontal with the inner ends of the pontoons being an appreciable distance above the bottom of the central drain I6.

The areas i9 between pontoons slope from the centers to the edge drain troughs 20 and the troughs slope to the central drain portion4 I6 in order that rain water and the like will ilow readily into the drain. Drain channels 2l are provided in the open areas I9 with these channels being formed in the roof bottom I4. and with each channel located at the side of a pontoon il. v The drain channelsl 20 lslope from the rim Il to the central drain I8. The areas I! between the pontoons i8, and also between the drain channels '20, are normaily bowed upward as shown in Figs. 2 and 4.

In order to provide for equalization of vapor over the bottom of the roof whenever there is any vapor formation, it is preferred that vapor lines 2i be provided. interconnecting the highest portions-of the roof bottom il, as is shown in Fig. 4. These vapor lines ordinarily connect the spaces beneath the tops oi the areas Il and the spaces beneath the pontoons Il.

Because the roof rests on top of the liquid. with its entire bottom surface in contact with the liquid. there will normally be very little or no vapor formed except on the very hottest days. When there is vapor formed it willbe equally distributed under the entire roof and escape oi the vapor from around the roof will be prevented by a depending-portion 22 of the rim il extending below the bottom surface of the roof.

One 'of the chief advantages of the new roo! is that it may be constructed much more easily and much more cheaply than-the ordinary roofs. In the ordinary construction oi the tank the pontoons can be built in the shop and tested there. The plate-like structure which forms thebottom of the roof can be built on the tank bottom, and the pontoons then installed. This makes the erection oi' the tank in the ileld very much cheaper and simpler.

Having described my invention as related to a typical embodiment of the same, it is my intention that the invention be not limited by the details of description unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

I claim:

1. A storage tank for liquids comprising a substantially cylindrical outer shell and a floating roof therein; said iloating roof comprising a substantially circular plate-like structure normally resting on top of the liquid, an upstanding vrim around said plate-like structure adjacent thel shell, a lowest drain portion located at substantially the center of said plate-like structure and forming a part thereof, a plurality of spaced airtight pontoons radiating from said lowest drain portion toward the rim and located above the liquid-contacting portion of said structure, and drain channels in the areas between the pontoons sloping to said lowest drain portion.

2. The storage tank of claim 1 wherein the pontoons are normally substantially horizontal and the areas between the pontoons are substantially horizontal and normally bowed laterally upward.

3. The storage tank of claim 1 wherein the tops of the pontoons do not extend substantially above the top edge of the rim.

4; The storage tank of claim 1 wherein the top loi' each pontoon slopes toward the sides.

5. The storage tank of claim 1 wherein the drain channels are located substantially at the sides of the pontoons. v

6. A storage tankfor liquids comprising a substantially cylindrical outer shell and a iioating roof therein, said oating roof comprising a substantially circular plate-like structure normally resting on top of the liquid, an upstanding rim around said plate-like structure adjacent the shell, a Ylowest drain portion located at substan,

tially the center of said plate-like structure and forming a part thereof, a plurality of spaced air` tight pontoons radiating from said lowest drain portion to the rim having their tops substantially level with the top edge of the rim with` the tops plate-like structure between adjacent pontoonsl being substantially horizontal and normally bowed laterally upward, and drain channels in the plate-like structure with each drain channel located at a side oi one of said pontoons and all drain channels sloping to the lowest drain portions oi' said structure.

7. A storage tank for liquids comprising an outer shell and a iioating root therein; said iloating roof comprising a plate-like structure normally resting on top of the liquid, a lowest drain portion located in said plate-like structure, a plurality oi spaced air-tight pontoons positioned around said lowest drain portion and located above the liquid-contacting portion ot said structure withthe areas between the pontoons being substantially horizontal and normally bowed laterally upward. drain channels in the areas between the pontoons sloping toward the lowest drain portion and being formed in the plate-like structure, and interconnected vapor lines connecting the highest portions oi said plate-like structure,

8. The storage tank of claim 6 wherein the Y areas of said plate-like structure between adjacent pontoons are normally curved upward between the drain channels.

9. The storage ltank of claim 6 wherein the areas of said plate-like structure between adjacent pontoons are normally curved upward between the drain channels and interconnecting vapor lines are provided connecting the highest portions of said plate-like structure.

10. The storage tank Aof claim 6 wherein the areas of said plate-like structure between adja cent pontoons are normally curved upward between the drain channels with the tops of said curved portions being substantially level with the bottoms of the pontoons, and interconnecting vapor lines are provided connecting the highest portions of said plate-like structures.

11.- The storage tank of claim 6 wherein the areas of said plate-like structure between adjacent pontoons are normally curved upward between the drain channels with the tops of said curved portions being substantially level with the bottoms ofthe pontoons, and interconnecting vapor lines are provided connecting the highest portions of said plate-like structures, said vapor lines connecting the spaces under said curved portions and the spaces under said pontoons.

JOHN W. ALLEN.

. REFERENCES CITED The following references are of record inthel ille of this patent:

4vUNITED STATES PATENTS 

